Fuel for internal combustion engines can vary for many reasons, such as seasonal blends and source (e.g., biodiesel). Compliance with various environmental regulations, improved fuel efficiency, improved engine performance, and the ability to adapt engine performance to various mixtures of fuels has been of increasing concern.
Some current fueling monitoring, diagnostics, and/or controls can incorporate closed-loop fueling algorithms. The mass of fuel removed from a pressurized volume may be calculated from the following equation:
                    m        =                                            ρ              ⁢                                                          ⁢              V                        β                    ⁢          Δ          ⁢                                          ⁢          P                                    Equation        ⁢                                  ⁢        1            where ρ is the fuel density, V is the pressurized volume, β is the bulk modulus of fuel in the pressurized volume, and ΔP is the pressure drop.
Using the bulk modulus equation:
                    c        =                              β            ρ                                              Equation        ⁢                                  ⁢        2            where c is the speed of sound, ρ is the fuel density, and β is the bulk modulus of fuel in the pressurized volume, we may be able to determine the mass removed from a pressurized volume in terms of the speed of sound, volume, and change in pressure, as illustrated by Equation 3 below:
                    m        =                              V                          c              2                                ⁢                      Δ            ⁢            P                                              Equation        ⁢                                  ⁢        3            
Because the sonic speed of a fluid may be dependent on fuel temperature, pressure, and fluid composition, the various conventional methods do not adequately monitor the mass of fuel removed from a pressurized volume, and they require a variety of various sensors monitoring pressure and temperature, which increases the cost, complexity, and maintenance of various engine components.
Moreover, many of these conventional methods and systems do not account for the fuel characteristics, such as blends, classifications, or temperature. Accordingly, when fuel tanks contain a variety of fuels (e.g., mixtures of biofuel and fossil fuels) or operate at varying temperatures, engine diagnostics, control, and performance can suffer.
A need therefore exists to address issues of more accurately determining the mass of fuel removed from pressurized volumes and determination of various characteristics of the fuel.